This invention relates generally to a method and device for cooling, preserving and safely transporting biological material such as equine semen specimens and equine embryos and particularly to such methods and devices that provide an optimum cooling rate and optimum steady state temperature for the cooled specimen.
Artificial insemination for improving livestock has long been a feature of animal husbandry. More recently, the suitability of some animal semen, such as that of bulls, for preservation by freezing has meant that specimens of such semen could be put into condition for preservation for relativey long periods of time, and be put into condition for easy transportation. As a result, it is relatively easy to provide such specimens for use at locations distant in time or place from the location where the specimen was originally obtained.
Equine artificial insemination has proven to be not so convenient. Equine semen appears to be much more sensitive to changes in temperature, to freezing, and to physical shock in transportation. In the case of equine semen, freezing the semen specimen for storage or transport results in a greatly decreased potency following thaw. Freezing appears to result in internal damage to the spermatozoa. In practice, typical post-thaw fertility is only 50-60%, whereas cooled but unfrozen semen has experimentally demonstrated a fertility rate of near 90% after 24 hours.
Furthermore, the post-warmup potency of equine semen depends strongly on the rate that it was cooled to achieve even the short term preservation of efficacy. Too rapid a temperature decrease results in thermal shock to the spermatozoa. Too slow a temperature change leaves the spermatozoa at high temperature for too long, causing decreased viability.
Many of the devices and methods used for preserving and transporting other kinds of biological material are therefore imappropriate for equine semen. The devices and methods often allow physical shock to the material, extremely low temperatures unsuitable for equine semen, uncontrolled rates of cooling, and time consuming procedures that do not take into account the relatively short time that equine semen remains viable after being obtained, even if cooled properly.
Therefore, ordinarily, mares are brought to a stud farm at great expense and inconvenience, rather than have equine semen specimens transported for any distance, because of the high rate of failure when such transportation has been attempted. Equine artificial insemination has therefore been, up until now. restricted in its use.
It is therefore an object of this invention to provide methods and devices for reliably preserving and safely transporting free from physical shock equine semen so that specimens may be preserved for commercially reasonable times (e.g. twenty-four hours) and be transportable in commercially reasonable means (e.g. trucks and planes).
It is also an object to provide a method and device for promptly cooling equine semen at an optimum controlled rate, and combining the cooling with transporting the specimen, so its eventual use elsewhere is shortened significantly. It is a further object to provide for achieving a steady state temperature for the cooled down specimen that is an optimum temperature for preservation of its efficacy.
It is a further object of the invention to provide such methods and devices that do not require chemicals for refrigation that must be controlled carefully to avoid contamination and harm, but rather may use the latent heat absorption in the phase change of common ice, even though an equine semen specimen should not be reduced in temperature to 0.degree. C.
It is a further object of the invention to provide a method for protection against physical shock, which is important for preservation of semen potency during its transportation.
Finally, it is an object of the invention to provide methods and devices for preserving and transporting equine semen that are inexpensive to manufacture from commonly available components and that are easy to use.
The invention is also useful for the cooling, preservation and storage of equine embryos, which require handling similar to equine semen, and, indeed, for other similar biological materials.